Lunar Glossary
| Crescent Moon | The shape of the lit portion of the moon or a planetary disk where the lit portion of the disk is less than half the disk surface. The terminator appear concave. |  Crescent Moon |
| Eclipse | An Eclipse occurs when one astronomical object moves into the shadow of another. The two types of eclipses of most interest to Earthlings, are Solar Eclipses when the Moon's shadow is cast across the surface of the Earth, and Lunar Eclipses where the Earth's shadow is cast onto the Moon. Lunar and Solar Eclipses usually occur two weeks from each other. Solar Eclipse always occur during a New Moon and Lunar Eclipses always occur during a Full Moon. | |
| First Quarter Moon | For the week between the New Moon and the First Quarter Moon the sunlit side of the Moon grows as a waxing (growing) crescent until the disk of the Moon is half lit. This half lit point is known as the First Quarter Moon. After the First Quarter the sunlit part of the Lunar disk is called waxing gibbous as it grows to illuminate the full disk of the Moon. |  First Quarter Moon |
| Full Moon | A Full Moon appears when the side on the moon facing Earth is completely sunlit. At this point the Moon is at Opposition to the Sun: rising as the Sun sets and setting as the Sun rises. If the Earth actually passes between the Sun and the Moon so that it's shadow passes across the Lunar surface that event would be a Lunar Eclipse. The Full Moon is typically the worse time for deep sky observing because the "moon glow" affects the dark sky. |  Full Moon |
| Gibbous Moon | The shape of the lit portion of the moon or a planetary disk where the lit portion of the disk is more than half the disk surface. The terminator appear convex. |  Gibbous Moon |
| Last Quarter Moon | The week between the Full Moon and the Last Quarter Moon the sunlit side of the Moon is called waning (shrinking) gibbous and is shrinking until the lunar disk is half in sunlight and half in shadow. This half lit point is the Last Quarter Moon. After the Last Quarter the sunlit side of the Moon continues to shrink as a waning crescent as the Moon approaches the Sun's position in the sky. |  Last Quarter Moon |
| New Moon | A New Moon occurs when the side on the moon facing Earth is completely in shadow. This means that the Moon and Sun are rising and setting in the same vicinity in the sky. If the Moon actually passes between the Sun and the Earth so that it's shadow passes across the Earth's surface that event would be a Solar Eclipse. New Moon is typically the very best time for deep sky observing. |  New Moon |
| Quarter Moon | One of two lunar phases when the moon's disk is half illuminated. The moon at this point is between crescent and gibbous phases. The First Quarter Moon the illuminate portion of the disk is "waxing" (growing larger each night) until the moon is "Full", and on the Last Quarter Moon the illuminated portion is "waning" (growing smaller each night) until the moon is "New". | Quarter Moon |
| Terminator | Boundary area between the lit and dark areas of the moon or planet. | |
| Waning Moon | The two week period from a Full to New Moon when the light across the surface of the moon is decreasing. | Waning Moon Movie |
| Waxing Moon | The two week period from a New to Full Moon when the light across the surface of the moon is increasing. | Waxing Moon Movie |
